this quote:

Last year, 12 people were killed in Lambeth, a gritty section of the city with a
growing reputation for gang warfare and drug dealing. But what alarms police and
community leaders even more is that half the murders were committed with guns,
increasingly the weapon of choice of criminals across Britain.

from this article explains one of the reasons to carry weapons. It is not whether you believe you have something that is worth your life but rather if someone else believes that they have a reason to threaten your life. If someone is willing to threaten your life - or the lives of your loved ones - then it is reasonable to be prepared to protect those lives with equal or greater force. I believe that I always have something worth someones life - My own life. If someone would attempt to take that from me I would want the ability to respond in kind.

Criminals killing people with firearms is the current best reason for non-criminals to be armed. The reason for the second ammendment was to ensure that the civilian population would be well enough armed to serve as a final check on unbridled governmental power. The threat of revolution from well armed and moderately trained civilian population that vastly outnumbers the government was intended to keep the government reminded of what we did to the last tyrant that tried to rule us unfairly. This is not something that is discussed all that often but it was important to the folks that passed the amendment. We didn't overthrow British tyrany just to fall prey to local dictators (or did we?).